1. Field of the Invention
The present invention relates to a driving method of an image sensor in an image sensing apparatus.
2. Description of the Related Art
In an image sensing apparatus such as a digital camera and video camera, an increase in frame rate of a continuous shooting speed of still images and moving image is demanded. Accordingly, it is required to shorten a signal readout time (total readout time) per frame of an image sensor used in the image sensing apparatus.
Japanese Patent Laid-Open No. 2009-89367 discloses a method of shortening the total readout time by shortening a blanking period (a period in which no signal is output from an image sensor). The arrangement of Japanese Patent Laid-Open No. 2009-89367 includes a first accumulation unit which holds signals output from respective pixel columns, and a second accumulation unit to which a signal in the first accumulation unit is transferred via a transfer unit such as a source-follower amplifier.
In a first period, a signal (that of a first pixel) in the first accumulation unit is transferred to the second accumulation unit. In a subsequent second period, the signal (signal of the first pixel) held in the second accumulation unit is read out to an output unit, and a signal of a next pixel (a signal of a second pixel) is transferred to the first accumulation unit. Thus, the total readout time is shortened.
However, in Japanese Patent Laid-Open No. 2009-89367, the first period (period in which a signal is transferred from the first accumulation unit to the second accumulation unit) is required in addition to the second period, and the total readout time is unnecessarily prolonged by that period.